1. Field of the Invention
The invention relates generally to devices for segregating and removing airborne dust and debris created during the crop harvesting process. More particularly, the invention pertains to a two-stage air/dust separator which processes and cleans the dirty air outputted by the suction fan used to separate crop from debris in an agricultural harvester.
2. Description of the Prior Art
Prior art harvesting machines typically employ a combination of gravitational and pneumatic forces to separate crop from commingled debris, mechanically collected from the ground during the harvesting process. This separation process generates a considerable amount of dust, debris, and airborne pollutants. U.S. Pat. No. 4,364,222, granted to Ramacher, shows a Nut Harvesting Machine employing the combination of a foraminous conveyor belt and a centrifugal suction fan. As shown in FIG. 1 of the '222 Patent, the discharge from the centrifugal fan, containing dust and debris which has been separated from the nut crop, is simply laterally discharged from the harvester into the air. The airborne pollutants may drift or be carried by wind currents to locations miles away from the orchard being harvested, causing health and environmental problems for the general public.
U.S. Pat. No. 5,421,147, issued to Holden et al., teaches a Nut Harvester including a scoop section within the lower portion of the centrifugal fan housing. The scoop section collects dirt and heavier debris passing through the fan housing and deposits them directly on the ground. The '147 Patent claims that through this partitioning action, dust emissions and airborne pollutants created during the harvesting process are minimized.
In another example of prior art efforts to control harvester air pollution, U.S. Pat. No. 6,036,600, granted to Kruckman, shows a Combine Dust Eliminator. An elongated dust eliminator housing has a pair of dust discharge chutes at either end. Fans are included to draw the contaminated air into the housing and drive it out a respective one of the discharge chutes. A “dust curtain” is provided at each discharge chute, to impede airborne dust outflow.
From the foregoing, it is apparent that the prior art recognizes the need to reduce harvester-caused air pollution. However, the devices known to Applicant either do not process the discharge sufficiently, or they require a relatively complex system of fans and large duct work to operate.
Thus, the need exists for an apparatus for cleaning air discharged from an agricultural harvester which effectively processes the discharge, but does not rely upon actively driven fans or other moving structures.
The need also exists for an air cleaning apparatus which is readily coupled to the existing air discharge from an agricultural harvester, and which can be mounted onto the existing frame of the harvester without extensive modifications.
The need also exists for an air cleaning apparatus having a two stage dust and debris separator, the first stage relying upon the centrifugal forces created by a centrifugal fan to separate dirty air from clean air, and the second stage relying upon a combination of residence time in a downwardly-directed labyrinth and gravitational forces to segregate debris, dirt and fine dust particles from clean air outputted to the atmosphere.
These and other objects of the present invention will be described in the drawings and in the detailed description of the preferred embodiment set forth below.